fix(deps): update gatsby monorepo

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
gatsby-plugin-sharp	2.13.0 -> 2.13.1
gatsby-source-contentful	4.5.0 -> 4.5.1

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Release Notes

gatsbyjs/gatsby

### [`v2.13.1`](https://togithub.com/gatsbyjs/gatsby/compare/03d497f15bc968d88bb0c85ce427da797b8fc61d...12a78aface75f7970c36a3d9c24a5d8dc5dd30c5) [Compare Source](https://togithub.com/gatsbyjs/gatsby/compare/fbc58933c6a6d5d8837e36104fdb74a0cb02163d...b6cac825e2044a9ca793fe057fcc6593d8f27d20)

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